This ANS-C01 practice question tests your understanding of network design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is designing a network for a multi-tier application. The web tier must be accessible from the internet, and the application tier must only be accessible from the web tier. Which architecture should they use?
Web servers in private subnets with a NAT Gateway for outbound traffic, and application servers in public subnets
Why wrong: Web servers need to be accessible from the internet, so they should be in public subnets.
B
Web servers in public subnets with an Internet Gateway, and application servers in private subnets with security groups allowing traffic only from the web tier
This follows best practices for multi-tier architectures.
C
All servers in a single VPC with VPC Peering to another VPC
Why wrong: VPC Peering is not relevant to tier isolation.
D
Web servers and application servers in public subnets, each with their own security group
Why wrong: Placing application servers in public subnets unnecessarily exposes them to the internet.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Web servers in public subnets with an Internet Gateway, and application servers in private subnets with security groups allowing traffic only from the web tier
Option A is correct because public subnets for web servers with Internet Gateway and private subnets for app servers with no direct internet access is standard. Option B is wrong because placing app servers in public subnets exposes them. Option C is wrong because NAT Gateway is for outbound, not inbound. Option D is wrong because VPC Peering is not needed.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Web servers in private subnets with a NAT Gateway for outbound traffic, and application servers in public subnets
Why it's wrong here
Web servers need to be accessible from the internet, so they should be in public subnets.
✓
Web servers in public subnets with an Internet Gateway, and application servers in private subnets with security groups allowing traffic only from the web tier
Why this is correct
This follows best practices for multi-tier architectures.
All servers in a single VPC with VPC Peering to another VPC
Why it's wrong here
VPC Peering is not relevant to tier isolation.
✗
Web servers and application servers in public subnets, each with their own security group
Why it's wrong here
Placing application servers in public subnets unnecessarily exposes them to the internet.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
Network Design — This question tests Network Design — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Web servers in public subnets with an Internet Gateway, and application servers in private subnets with security groups allowing traffic only from the web tier — Option A is correct because public subnets for web servers with Internet Gateway and private subnets for app servers with no direct internet access is standard. Option B is wrong because placing app servers in public subnets exposes them. Option C is wrong because NAT Gateway is for outbound, not inbound. Option D is wrong because VPC Peering is not needed.
What should I do if I get this ANS-C01 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related ANS-C01 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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